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Cool and hot eruptions, worlds apart

Rings over Etna. copyright Tom Pfeiffer –

Volcanic Mount Sinbung in Sumatra, Indonesia, has sprung to life in a series of massive eruptions over the last few days. The volcano had lain dormant for more than 400 years before a few minor eruptions three years ago. But this week more than 5,000 people have been evacuated from nearby towns and villages as Sinbung makes her presence felt.

As Sinabung puts on her show of power, in the Mediterranean the volcano Etna has also been active this week. But the view of Etna’s summit is far more gentle, as extraordinary smoke rings have been puffed into the Sicilian sky, as if the volcano is sitting back and relaxing for a while. Photographer Tom Pfeiffer managed to capture the scene with a series of fantastic shots.

Puffing away. copyright Tom Pfeiffer

Steam rising. copyright Tom Pfeiffer

The Indonesian volcano, however, erupted an ash cloud more than four miles into the air. A super-heated avalanche of lava, ash and rock raced down its flanks at terrifying speeds on Monday. There are reports of a stream of red hot lava extending a kilometre or so from the vent.

Sinabung’s activity is fed by the slow tectonic descent of rocks forming the floor of the Indian ocean, drawn down and northward into Earth’s mantle beneath Indonesia. This geological feature is called the “Sunda Arc” and it is home to some of the largest volcanic eruptions ever seen.

While Sineburg rages, Etna chills; copyright Tom Pfeiffer

The 1815 eruption of Mount Tambara, above the Sunda Arc, remains the largest recorded volcano ever. But it is topped by the super-eruption of Toba, also in Sumatra, which scientists place at 70,000 years ago as the largest in human history. The eruption of Indonesian Krakatoa was smaller than both, yet was heard 3,000 miles away and caused widespread devastation and more than 35,000 deaths.

Indonesia, the world’s fourth most populous nation, sits atop a geological powder keg. This week’s eruption of Sinabung serves as a reminder.

The Conversation

This article was originally published at The Conversation.
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Simon Redfern is a mineral physicist at the University of Cambridge. He studies the properties of materials in Earth, from biominerals in seas shells to the nature of Earth's inner core. He uses neutron and synchrotron light sources to study these properties at the atomic scale, and links the results to phenomena at the global scale. Tweets as @Sim0nRedfern.